Optical Power Budget of 25+ Gbps IM/DD PON with Digital Signal Post-Equalization

Aleksejs Udalcovs,Sandis Spolitis,Lu Zhang,Anders Djupsjöbacka,Oskars Ozolins,Xiaodan Pang,Vjaceslavs Bobrovs,Sergei Popov,Toms Salgals

doi:10.3390/app10176106

Abstract

While infrastructure providers are expanding their portfolio to offer sustainable solutions for beyond 10 Gbps in the access segment of optical networks, we experimentally compare several modulation format alternatives for future passive optical networks (PONs) aiming to deliver 25+ Gbps net-rates. As promising candidates, we consider the intensity modulation direct detection (IM/DD) schemes such as electrical duobinary (EDB) and 4-level and 8-level pulse amplitude modulations (PAM-4/8). They are more spectrally efficient than the conventional non-return-to-zero on-off-keying (NRZ-OOK) used in current 10G PONs. As we move to higher rates, digital equalization enhances the performance by smoothening the systems imperfection. However, the impact that such equalization has on the optical power budget remains unclear. Therefore, in this article, we fairly compare the optical power budget values of a time division multiplexed PON (TDM-PON) exploiting a linear digital signal equalization at the receiver side. We consider the conventional PON configuration (20 km of single-mode fiber (SMF), 1:N optical power splitting) with IM/DD and net-rates above 25 Gbps. Furthermore, we focus on a downstream transmission imposing the bandwidth limitations of 10G components using a digital filter before the detection. The obtained results show that the use of a digital post-equalization with 43 feed-forward (FF) and 21 feedback (FB) taps can significantly improve the signal quality enabling new alternatives and enhancing the optical power budget.

Highlights

An immense range of mobile and broadband services, such as Netflix, Spotify, etc., provoke an unprecedented growth of consumer-driven data consumption, which leads to an increase of bandwidth demands in fiber-optic access networks [1]
As we limit the receiver’s bandwidth to 8 GHz, we investigate whether components intended for the 10G operation can be used for 25+ Gbps operation
The applied low-pass filtering (LPF) is imposed to emulate the bandwidth limitations at the receiver’s (Rx) side aiming to investigate whether components intended for the 10G operation can be used for higher line rates

Summary

Introduction

An immense range of mobile and broadband services, such as Netflix, Spotify, etc., provoke an unprecedented growth of consumer-driven data consumption, which leads to an increase of bandwidth demands in fiber-optic access networks [1]. As 10G PON systems are not capable support future services, especially in the context of the fifth generation (5G) mobile networks, 25G is the evolution step that must be taken [2]. It is not clear which means will be used to make it

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